Method and apparatus for humidification



Sept. 2, 1969 w. L. M GRATH 3,464,401

METHOD AND APPARATUS FOR HUMIDIFICATION Filed Nov. 15, 1967 0 k '9 l5 I ESIRED RELATIVE SIG. 5

25 RELATIVE DITY FIG. 2 1k HUMIDITY 35 II, I. 23 I o Z EXTERIOR TEMP. -I

9 I00 37 I? /E um ON TIME \E o y 15 EXTERIOR TEMP. --l0 20o"- g P 4 FURNACE TEME I5 fl 2 32 29 5 EXTERIOR TEMP INVENTOR. 33 27 3 WILLIAM L. Mc GRATH.

I a 3 BY?QMA4 i M 7 ATTORNEY.

3,464,401 METHOD AND APPARATUS FOR HUMIDIFICATION William L. McGrath, Syracuse, N.Y., assignor to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed Nov. 15, 1967, Ser. No. 683,206 Int. (1]. F24f 3/14 US. Cl. 1261l3 2 Claims ABSTRACT OF THE DISCLOSURE A humidifier adapted for use with a forced air furnace having a thermally operated water supply valve for operating the humidifier to provide a decreasing relative humidity in the conditioned area as exterior temperatures decrease.

BACKGROUND OF THE INVENTION Humidification of the air in homes and other structures is often necessary during the heating season. One of the simplest ways of achieving this is to provide a pan of water in the hot air plenum of a furnace. However, the water surface exposed to the Warm air is limited by the size of the plenum.

Numerous mechanisms have been devised to increase the evaporative surface exposed to the hot air. One of the common types employs a disc or wheel of an absorbent material having a portion submerged in a water reservoir, rotation of the disc continually presenting a wetted surface to the hot air stream for evaporation of the water thereon. Rotation of the disc is usually accomplished by an elertric motor which is connected in the furnace fan circuit so as to operate only when there is air movement through the plenum. A further refinement of this type of system includes a humidistat in the disc motor circuit to prevent rotation of the disc even though the fan is operating if there is sufiicient moisture in the area served by the furnace. However, even this described method does not provide a completely acceptable system.

As exterior temperature drops, the moisture requirements in the conditioned area ordinarily increase. However, it is not feasible to maintain the same relative humidity within the area under varying exterior tempera ture conditions as objectionable moisture will condense on cold surfaces such as windows if area relative humidity is not lowered as the exterior temperature drops. For optimum performance of this type of system, a humidistat that is also responsive to exterior temperatures is desirable.

As can be seen from the foregoing, a rather complicated and expensive system is necessary for satisfactory humidification of the area being conditioned.

SUMMARY OF THE INVENTION This invention relates to a humidifier employing a temperature responsive valve to provide humidifier operation proportional to exterior temperature as reflected by burner operating time.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of a humidifier with parts broken away for clarity;

FIGURE 2 is a sectional view of the humidifier;

FIGURE 3 is a graph of furnace plenum temperatures over a period of time during decreasing exterior temperatures;

FIGURE 4 is a graph illustrating the percentage of burner operation and the percentage of humidifier oper- 3,464,401 Patented Sept. 2, 1969 ation necessary to provide desired area humidity conditions during decreasing exterior temperature; and

FIGURE 5 is a graph of desired relative humidity in the conditioned area in relation to exterior temperature.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is illustrated a humidifier casing 2 having an inlet 5 and an outlet 7 for passage of heated air as shown by the solid arrows from the hot air plenum through an evaporative pad 9 in casing to the return air duct of a forced air furnace. A damper 8 is provided in outlet 7 to obtain the desired quantity of air fiow through the casing. The air flow through the casing can also be reversed as shown by the dotted arrows. This air flow arrangement provides humidified air to the furnace return air plenum for passage through the furnace and the Warm air distribution system to the area being conditioned. While this arrangement results in a portion of the heated air bypassing the normal air distribution system, it provides a positive pressure differential across the humidifier casing to assure a relatively constant air flow therethrough.

Water to be evaporated is supplied to the humidifier through line 11, water control valve 13 and jet pump 15. Water from jet pump 15 flows through line 17 to upper reservoir 19 which is provided with a dumping siphon 21. When the water level in the upper reservoir reaches the top of siphon 21, the water is siphoned into a distribution tray 23 which is provided with notches or weirs 25 for distributing the water in the tray evenly over evaporative pad 9 for evaporation by the air stream passing therethrough. Excess water from the pad drains into lower reservoir 27. A portion of the water in lower reservoir is pumped back to upper reservoir 19 by jet pump 15 which is provided with a pickup line 29 having a strainer 31 associated therewith. The jet pump is so sized that it induces about 3 parts of water from the lower reservoir for each part of water supplied through valve 13. Even though water in the lower reservoir is being constantly pumped to the upper reservoir, the water level in the lower reservoir continually rises until it covers the dump siphon 32 associated therewith. When this occurs the water in the lower reservoir is siphoned to drain, thereby removing collected dirt and scale particles in the lower reservoir and preventing a high mineral concentration in the recirculating water. Small apertures 33 are provided in both siphons to break the siphoning action at the desired water level to prevent complete draining of the reservoirs while maintaining the end of the siphons near the bottom of the reservoirs to assure removal of dirt particles collecting thereon.

Thermal valve 13 includes a liquid fill system comprising a bellows (not shown) connected by capillary 37 to a bulb 35 which reflects the temperature of the air passing through the humidifier casing. Warm air passing in heat exchange relation with bulb- 35 actuates the bellows to move the valve toward an open position to allow passage of water to the humidifier evaporative media for evaporation therefrom. An adjustment screw 39 on valve 13 allows the valve opening temperature to be adjusted to obtain the desired humidifier operating time in relation to burner operating time. This allows the system to be adjusted according to the moisture requirements of each installation.

Considering the operation of the humidifier in conjunction with a forced air furnace, air flow through the humidifier from the hot air plenum of the furnace to the cold air plenum is provided by the pressure differential created therebetween by the furnace fan. For optimum comfort in the area being heated, it is desirable to size the furnace output, fan speeds, and fan running time to provide substantially continuous fan operation. Under these conditions, there is a substantially continuous flow of air through the humidifier.

To provide the optimum humidification of the area being conditioned while avoiding moisture condensation on cold surfaces such as windows, the relative humidity of the area should be decreased as exterior temperature decreases. However, as exterior temperature decreases, the quantity of moisture necessary to provide the desired relative humidity in the conditioned. area increases. Since the furnace burner will cycle under control of the room thermostat to maintain a desired temperature in the conditioned area, as exterior temperature decreases, the burner operating time will increase. Thus, there is an increase in burner operating time under the same conditions that require an increase in the quantity of moisture supplied to the area being heated.

Since the temperature of the air flowing through the humidifier varies in response to the burner cycles, the humidifier operation can be coordinated with the plenum air temperature so as to increase the humidifier operating time and therefore the quantity of moisture supplied to the conditioned area as exterior temperature drops. Further, it is possible to coordinate the humidifier operating period with the plenum air temperature to provide a decrease in relative humidity in the conditioned area as exterior temperatures decrease to prevent harmful condensation in the conditioned area. This is accomplished through the operation of the thermally controlled water valve. Due to the variation in moisture requirements between various humidifier installations, there is a definite humidifier operating time in relation to burner operating time in each nstallation that will provide proper humidification of the area. For this reason, the tempera ture at which valve 13 opens may be adjusted for increasing or decreasing humidifier operation in relation to burner operation. The foregoing may be more easily understood by referring to FIGURE 3 of the drawing, which graphically illustrates the relationship between furnace and humidifier operation.

In FIGURE 3, line T represents the fan on temperature and curve P represents the plenum temperature variations due to the cyclical operation of the burner. The curve P has been drawn to illustrate decreasing exterior temperatures over a period of time.

Line H represents the temperature above which the humidifier will operate. As can be seen from the relationship of the line H and curve P as the exterior temperature decreases, humidifier operation will. increase. If it is desired to provide increased humidification to the area, the valve can be adjusted to open at a lower temperature, for example, at the temperature represented by line H As can be seen from the figure, this increases the operating time of the humidifier and therefore the quantity of water supplied to the air flowing therethrough.

The relationship of the percentage of burner operating time and the percentage of humidifying load relative to exterior temperature is shown in FIGURE 4 and the desired inside relative humidity in relation to exterior tem perature is shown in FIGURE 5. As can be seen from FIGURES 4 and 5, as exterior temperatures decrease, the percentage of burner operating time and the humidifying load increases while the desired inside relative humidity decreases. Since the curves of the percentage of burner on time and percentage of humidifying load are both subtantially linear, the temperature at which the humidifier valve opens may be selected so that under decreasing exterior temperature conditions, there is an increase in the quantity of moisture supplied to the conditioned area which Will be insufficient to maintain a constant relative humidity therein but will result in a desired decrease in relative humidity.

While I have described a preferred embodiment of the invention, it is to be understood the invention is not limited thereto but may be otherwise embodied within the scope of the following claims:

I claim:

1. A method for maintaining the desired humidity in an area served by a forced air furnace including the steps of:

forcing air through the furnace after a predetermined burner operating time interval,

passing a portion of the air from the furnace over an evaporative contact media, and

supplying water to the evaporative contact media in response to a predetermined furnace bonnet temperature higher than that existing in the furnace at the end of said predetermined burner operating time interval to provide humidifier operation for a period of time less than the fan operating time, said water being evaporated from the media by the air passing thereover.

2. A humidifier for use with a forced air furnace employing a fan switch to energize the fan after a predetermined burner operating time interval comprising:

a casing adapted for passage of air therethrough,

an evaporative media disposed in said casing,

means for passing heated air through said media,

a water valve for regulating the flow of water to said evaporative media, and

actuating means for said valve including a thermoresponsive element disposed in the path of the heated air stream to open said valve in response to a predetermined temperature of the air stream higher than that existing at the end of the predetermined burner operating time interval.

References Cited UNITED STATES PATENTS 1,848,327 3/1932 Dudley et al. 2,075,314 3/1937 Suppes 1261l3 x 2,105,773 1/1938 Magney 126113 X 3,265,371 8/1966 McGrath 126113 X JAMES W. WESTHAVER, Primary Examiner U.S. Cl. X.R. 236--44; 261-27 

